I'm proud to give you here a full tutorial in french and english for building completly ZCS 6 GA on Ubuntu Server (32 or 64 bits).
So here french tuto :
Comment installer Zimbra Server 6 (Release) sur Ubuntu Server 9.04 (Jaunty) ! | Celogeek
here english tuto :
How to install Zimbra Server 6 (Release) on Ubuntu Server 9.04 (Jaunty) ! | Celogeek
At the end of the tutorial, you can get the result version I have made from my tutorial. It's an RTU package.
Just get it and install !
Happy tuto and download,